| 1. |
- Kristanl, Matej, et al.
(författare)
-
The Seventh Visual Object Tracking VOT2019 Challenge Results
- 2019
-
Ingår i: 2019 IEEE/CVF INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW). - : IEEE COMPUTER SOC. - 9781728150239 ; , s. 2206-2241
-
Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2019 is the seventh annual tracker benchmarking activity organized by the VOT initiative. Results of 81 trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in the recent years. The evaluation included the standard VOT and other popular methodologies for short-term tracking analysis as well as the standard VOT methodology for long-term tracking analysis. The VOT2019 challenge was composed of five challenges focusing on different tracking domains: (i) VOT-ST2019 challenge focused on short-term tracking in RGB, (ii) VOT-RT2019 challenge focused on "real-time" short-term tracking in RGB, (iii) VOT-LT2019 focused on long-term tracking namely coping with target disappearance and reappearance. Two new challenges have been introduced: (iv) VOT-RGBT2019 challenge focused on short-term tracking in RGB and thermal imagery and (v) VOT-RGBD2019 challenge focused on long-term tracking in RGB and depth imagery. The VOT-ST2019, VOT-RT2019 and VOT-LT2019 datasets were refreshed while new datasets were introduced for VOT-RGBT2019 and VOT-RGBD2019. The VOT toolkit has been updated to support both standard short-term, long-term tracking and tracking with multi-channel imagery. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The dataset, the evaluation kit and the results are publicly available at the challenge website(1).
|
|
| 2. |
- Kristan, Matej, et al.
(författare)
-
The Sixth Visual Object Tracking VOT2018 Challenge Results
- 2019
-
Ingår i: Computer Vision – ECCV 2018 Workshops. - Cham : Springer Publishing Company. - 9783030110086 - 9783030110093 ; , s. 3-53
-
Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2018 is the sixth annual tracker benchmarking activity organized by the VOT initiative. Results of over eighty trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in the recent years. The evaluation included the standard VOT and other popular methodologies for short-term tracking analysis and a “real-time” experiment simulating a situation where a tracker processes images as if provided by a continuously running sensor. A long-term tracking subchallenge has been introduced to the set of standard VOT sub-challenges. The new subchallenge focuses on long-term tracking properties, namely coping with target disappearance and reappearance. A new dataset has been compiled and a performance evaluation methodology that focuses on long-term tracking capabilities has been adopted. The VOT toolkit has been updated to support both standard short-term and the new long-term tracking subchallenges. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The dataset, the evaluation kit and the results are publicly available at the challenge website (http://votchallenge.net).
|
|
| 3. |
- Duan, Lele, et al.
(författare)
-
Ce-IV- and Light-Driven Water Oxidation by [Ru(terpy)(pic)(3)](2+) Analogues : Catalytic and Mechanistic Studies
- 2011
-
Ingår i: CHEMSUSCHEM. - : Wiley. - 1864-5631. ; 4:2, s. 238-244
-
Tidskriftsartikel (refereegranskat)abstract
- A series of mononuclear ruthenium polypyridyl complexes [Ru(Mebimpy)(pic)(3)](PF6)(2) (2; Mebimpy=2,6-bis(1-methylbenzimidazol-2-yl)pyridine; pic=4-picoline), Ru(bimpy)(pic)(3) (3; H(2)bimpy=2,6-bis(benzimidazol-2-yl)pyridine), trans-[Ru(terpy)-(pic)(2)Cl](PF6) (4; terpy=2,2';6',2 ''-terpyridine), and trans-[Ru(terpy)(pic)(2)(OH2)](ClO4)(2) (5) are synthesized and characterized as analogues of the known Ru complex, [Ru(terpy)(pic)(3)](PF6)(2) (1). The effect of the ligands on electronic and catalytic properties is studied and discussed. The negatively charged ligand, bimpy(2-), has a remarkable influence on the electrochemical events due to its strong electron-donating ability. The performance in light- and Ce-IV-driven (Ce-IV=Ce(NH4)(2)(NO3)(6)) water oxidation is successfully demonstrated. We propose that ligand exchange between pic and H2O occurs to form the real catalyst, a Ru-aqua complex. The synthesis and testing of trans[Ru(terpy)(pic)(2)(OH2)](ClO4)(2) (5) confirmed our proposal. In addition, complex 5 possesses the best catalytic activity among these five complexes.
|
|
| 4. |
- Duan, Lele, et al.
(författare)
-
Chemical and Photochemical Water Oxidation Catalyzed by Mononuclear Ruthenium Complexes with a Negatively Charged Tridentate Ligand
- 2010
-
Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 16:15, s. 4659-4668
-
Tidskriftsartikel (refereegranskat)abstract
- Two mononuclear ruthenium complexes [RuL(pic)(3)] (1) and [RuL(bpy)(pic)] (2) (H2L = 2,6-pyridinedicarboxylic acid, pic=4-picoline, bpy = 2,2'-bipyridine) have been synthesized and fully characterized. Both complexes could promote water oxidation chemically and photochemically. Compared with other known ruthenium-based water oxidation catalysts using [Ce(NH4)(2)(NO3)(6)] (Ce-IV) as the oxidant in solution at pH 1.0, complex 1 is one of the most active catalysts yet reported with an initial rate of 0.23 turnovers(-1). Under acidic conditions, the equatorial 4-picoline in complex 1 dissociates first. In addition, ligand exchange in 1 occurs when the Rum state is reached. Based on the above observations and MS measurements of the intermediates during water oxidation by 1 using Ce-IV as oxidant, [RuL(pic)(2)(H2O)](+) is proposed as the real water oxidation catalyst.
|
|
| 5. |
|
|
| 6. |
- Duan, Lele, et al.
(författare)
-
Isolated Seven-Coordinate Ru(IV) Dimer Complex with HOHOH (-) Bridging Ligand as an Intermediate for Catalytic Water Oxidation
- 2009
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:30, s. 10397-
-
Tidskriftsartikel (refereegranskat)abstract
- With the inspiration from an oxygen evolving complex (OEC) in Photosystern II (PSII), a mononuclear Ru(II) complex with a tetradentate ligand containing two carboxylate groups has been synthesized and structurally characterized. This Ru(II) complex showed efficient catalytic properties toward water oxidation by the chemical oxidant cerium(IV) ammonium nitrate. During the process of catalytic water oxidation, Ru(III) and Ru(IV) species have been successfully isolated as intermediates. To our surprise, X-ray crystallography together with HR-MS revealed that the Ru(IV) species is a seven-coordinate Ru(IV) dimer complex containing a [HOHOH](-) bridging ligand. This bridging ligand has a short O center dot center dot center dot O distance and is hydrogen bonded to two water molecules. The discovery of this very uncommon seven-coordinate Ru(IV) dimer together with a hydrogen bonding network may contribute to a deeper understanding of the mechanism for catalytic water oxidation. It will also provide new possibilities for the design of more efficient catalysts for water oxidation, which is the key step for solar energy conversion into hydrogen by tight-driven water splitting, the ultimate challenge in artificial photosynthesis.
|
|
| 7. |
- Duan, Lele, et al.
(författare)
-
Visible Light-Driven Water Oxidation by a Molecular Ruthenium Catalyst in Homogeneous System
- 2010
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 49:1, s. 209-215
-
Tidskriftsartikel (refereegranskat)abstract
- Discovery of an efficient catalyst bearing low overpotential toward water oxidation is a key step for light-driven water splitting into dioxygen and dihydrogen. A mononuclear ruthenium complex, Ru(II)L(pic)(2) (1) (H2L = 2,2'-bipyridine-6,6'-dicarboxylic acids pic = 4-picoline), was found capable of oxidizing water eletrochemically at a relatively low potential and promoting light-driven water oxidation using a three-component system composed of a photosensitizer, sacrificial electron acceptor, and complex 1. The detailed electrochemical properties of 1 were studied, and the onset potentials of the electrochemically catalytic curves in pH 7.0 and pH 1.0 solutions are 1.0 and 1.5 V, respectively. The low catalytic potential of 1 under neutral conditions allows the use of [Ru(bpy)(3)](2+) and even [Ru(dmbpy)(3)](2+) as a photosensitizer for photochemical water oxidation. Two different sacrificial electron acceptors, [Co(NH3)(5)Cl]Cl-2 and Na2S2O8, were used to generate the oxidized state of ruthenium tris(2,2'-bipyridyl) photosensitizers. In addition, a two-hour photolysis of I in a pH TO phosphate buffer did not lead to obvious degradation, indicating the good photostability of our catalyst. However, under conditions of light-driven water oxidation, the catalyst deactivates quickly. In both solution and the solid state under aerobic conditions, complex 1 gradually decomposed via oxidative degradation of its ligands, and two of the decomposed products, sp(3) C-H bond oxidized Ru complexes, were identified. The capability of oxidizing the sp(3) C-H bond implies the presence of a highly oxidizing Ru species, which might also cause the final degradation of the catalyst.
|
|
| 8. |
- Duan, Lele, et al.
(författare)
-
Visible light-driven water oxidation-from molecular catalysts to photoelectrochemical cells
- 2011
-
Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 4:9, s. 3296-3313
-
Tidskriftsartikel (refereegranskat)abstract
- This perspective article reports the most significant advances in the field of water oxidation-from molecular water oxidation catalysts (WOCs) to photoelectrochemical cells. Different series of catalysts that can be applied in visible light-driven water oxidation catalysis are discussed in details and several key aspects of their catalytic mechanisms are introduced. In order to construct a water oxidation electrode from molecular catalysts, proper immobilization methods have to be employed. Herein, we present one section about how to attach catalysts onto an electrode/material surface. Finally, the state of the art photoelectrochemical cells that achieve visible light-driven water splitting are described.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Lee, Bao-Lin, 1976-, et al.
(författare)
-
Synthesis and characterization of oligonuclear Ru, Co, and Cu oxidation catalysts
- 2010
-
Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :34, s. 5462-5470
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we report the preparation and crystal structures of three new oligonuclear complexes, Ru-2(bbpmp)(mu-OAc)(3) (4), [Co-2(bbpmp)(mu-OAc)(mu-OMe)](PF6) (5), [Cu-4(Hbbpmp)(2)(mu-OAc)(H2O)(2)](OAc)(PF6)(2) (6) {H(3)bbpmp = 2,6-bis[(2-hydroxybenzyl)-(2-pyridylmethyl)aminomethyl]-4-methylphenol (3)}. The structures of the complexes were determined by single-crystal X-ray diffraction. The oxidation states of ruthenium, cobalt and copper in the complexes are +3, +3 and +2, respectively. In 4 and 5, Ru-III and Co-III are coordinated to four oxygen and two nitrogen atoms in an octahedral geometry, while in 6, Cu-II adopts both octahedral (CuN2O4) and square-pyramidal (CuN2O3) geometry. The potential of the three complexes as oxidation catalysts has been investigated.
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
- Nonomura, Kazuteru, et al.
(författare)
-
The effect of UV-irradiation (under short-circuit condition) on dye-sensitized solar cells sensitized with a Ru-complex dye functionalized with a (diphenylamino)styryl-thiophen group
- 2009
-
Ingår i: International Journal of Photoenergy (Online). - : Hindawi Limited. - 1110-662X .- 1687-529X. ; :471828
-
Tidskriftsartikel (refereegranskat)abstract
- A new ruthenium complex, cis-di(thiocyanato)(2,2'-bipyridine-4,4'-dicarboxylic acid)(4,4'-bis(2-(5-(2-(4-diphenylaminophenyl) ethenyl)-thiophen-2-yl)ethenyl)-2,2'-bipyridine)ruthenium(II) (named E322) has been synthesized for use in dye-sensitized solar cells (DSCs). Higher extinction coeff. and a broader absorption compared to the std. Ru-dye, N719, were aimed. DSCs were fabricated with E322, and the efficiency was 0.12% initially (4.06% for N719, as ref.). The efficiency was enhanced to 1.83% by exposing the cell under simulated sunlight contg. UV-irradn. at short-circuit condition. The reasons of this enhancement are (1) enhanceing electron injection from sensitizer to TiO2 following a shift toward pos. potentials of the conduction band of TiO2 by the adsorption of protons or cations from the sensitizer, or from the redox electrolyte and (2) improving the regeneration reaction of the oxidized dye by the redox electrolyte by the dissoln. of aggregated dye from the surface of TiO2 following the treatment.
|
|
| 17. |
|
|
| 18. |
|
|
| 19. |
- Pettersson, Henrik, et al.
(författare)
-
Parallel-connected monolithic dye-sensitised solar modules
- 2010
-
Ingår i: Progress in Photovoltaics. - : Wiley. - 1062-7995 .- 1099-159X. ; 18:5, s. 340-345
-
Tidskriftsartikel (refereegranskat)abstract
- Light-soaking and high-temperature storage testing of monolithic dye-sensitised solar modules with total area module efficiencies above 5% have been performed. Our experiences from the development of a four-layer monolithic dye-sensitised solar test cell for comparative testing of material components for dye-sensitised solar cells have directed our module development to a novel device design consisting of parallel-connection of individual monolithic cells. The results from the accelerated testing of the modules (total area of 17.0 cm(2)) with four parallel-connected cells (active area of 3.38 cm(2)/cell) are equivalent to those obtained for the monolithic single test cells when using identical device components. The successful transfer from cell to module stability is an important milestone in our ambition to develop a low-cost Photovoltaic (PV) technology. Moreover, our results indicate that intensified research and development to define the procedures for relevant accelerated testing of dye-sensitised solar modules is urgently required.
|
|
| 20. |
- Sjödin, Martin, et al.
(författare)
-
Switching the redox mechanism : Models for proton coupled electron transfer from tyrosine and tryptophan
- 2005
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 127:11, s. 3855-3863
-
Tidskriftsartikel (refereegranskat)abstract
- The coupling of electron and proton transfer is an important controlling factor in radical proteins, such as photosystem II, ribinucleotide reductase, cytochrome oxidases, and DNA photolyase. This was investigated in model complexes in which a tyrosine or tryptophan residue was oxidized by a laser-flash generated trisbipyridine-Ru-III moiety in an intramolecular, proton-coupled electron transfer (PCET) reaction. The PCET was found to proceed in a competition between a stepwise reaction, in which electron transfer is followed by deprotonation of the amino acid radical (ETPT), and a concerted reaction, in which both the electron and proton are transferred in a single reaction step (CEP). Moreover, we found that we could analyze the kinetic data for PCET by Marcus' theory for electron transfer. By altering the solution pH, the strength of the Ru-III oxidant, or the identity of the amino acid, we could induce a switch between the two mechanisms and obtain quantitative data for the parameters that control which one will dominate. The characteristic pH-dependence of the CEP rate (M. Sjodin et al. J. Am. Chem. Soc. 2000, 122, 3932) reflects the pH-dependence of the driving force caused by proton release to the bulk. For the pH-independent ETPT on the other hand, the driving force of the rate-determining ET step is pH-independent and smaller. On the other hand, temperature-dependent data showed that the reorganization energy was higher for CEP, while the pre-exponential factors showed no significant difference between the mechanisms. Thus, the opposing effect of the differences in driving force and reorganization energy determines which of the mechanisms will dominate. Our results show that a concerted mechanism is in general quite likely and provides a low-barrier reaction pathway for weakly exoergonic reactions. In addition, the kinetic isotope effect was much higher for CEP (k(H)/k(D) > 10) than for ETPT (k(H)/k(D) = 2), consistent with significant changes along the proton reaction coordinate in the rate-determining step of CEP.
|
|
| 21. |
|
|
| 22. |
- Tong, Lianpeng, et al.
(författare)
-
Water Oxidation Catalysis : Influence of Anionic Ligands upon the Redox Properties and Catalytic Performance of Mononuclear Ruthenium Complexes
- 2012
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 51:6, s. 3388-3398
-
Tidskriftsartikel (refereegranskat)abstract
- Aiming at highly efficient molecular catalyts for water oxidation, a mononuclear ruthenium complex Ru-II(hqc)(pic)(3) (1; H(2)hqc = 8-hydroxyquinoline-2-carboxylic acid and plc = 4-picoline) containing negatively charged carboxylate and phenolate donor groups has been designed and synthesized. As a comparison, two reference complexes, Ru-II(pdc)(pic)(3) (2; H(2)pdc = 2,6-pyridine-dicarboxylic acid) and Ru-II(tpy)(pic)(3) (3; tpy = 2,2':6',2 ''-terpyridine), have also been prepared. All three complexes are fully characterized by NMR, mass spectrometry (MS), and X-ray crystallography. Complex 1 showed a high efficiency toward catalytic water oxidation either driven by chemical oxidant (Ce-IV in a pH 1 solution) with a initial turnover number of 0.32 s(-1), which is several orders of magnitude higher than that of related mononuclear ruthenium catalysts reported in the literature, or driven by visible light in a three-component system with [Ru(bpy)(3)](2+) types of photosensitizers. Electrospray ionization MS results revealed that at the Rum state complex 1 undergoes ligand exchange of 4-picoline with water, forming the authentic water oxidation catalyst in situ. Density functional theory (DFT) was ernployed to explain how anionic ligands (hqc and pdc) facilitate the 4-picoline dissociation compared with a neutral ligand (tpy). Electrochemical measurements show that complex 1 has a much lower E(Ru-III/Ru-II) than that of reference complex 2 because of the introduction of a phenolate ligand. DFT was further used to study the influence of anionic ligands upon the redox properties of mononuclear aquaruthenium species, which are postulated to be involved in the catalysis cycle of water oxidation.
|
|
| 23. |
- Xu, Yunhua, et al.
(författare)
-
A New Dinuclear Ruthenium Complex as an Efficient Water Oxidation Catalyst
- 2009
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 48:7, s. 2717-2719
-
Tidskriftsartikel (refereegranskat)abstract
- A dinuclear ruthenium complex, which acts as a molecular catalyst for water oxidation, has been synthesized and characterized. The electronic and electrochemical properties were studied by UV-vis spectroscopy and cyclic voltammetry. The oxidation potentials of the complex are significantly lowered by introducing a negatively charged carboxylate ligand, in comparison with those of the reported complexes that have neutral ligands. The catalytic activity of the complex toward water oxidation using Ce(NH4)(2)(NO3)(6) as a chemical oxidant was investigated by means of an oxygen electrode and mass spectrometry. The turnover number of this catalyst with Ce-IV as the chemical oxidant was found to be ca. 1700. The mass spectroscopic analysis of the isotopomer distribution in oxygen evolved from O-18-labeled water indicates that O atoms in the evolved oxygen originate from water.
|
|
| 24. |
|
|
| 25. |
- Xu, Yunhua, et al.
(författare)
-
Synthesis and Catalytic Water Oxidation Activities of Ruthenium Complexes Containing Neutral Ligands
- 2011
-
Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 17:34, s. 9520-9528
-
Tidskriftsartikel (refereegranskat)abstract
- Two dinuclear and one mononuclear ruthenium complexes containing neutral polypyridyl ligands have been synthesised as pre-water oxidation catalysts and characterised by (1)H and (13)C NMR spectroscopy and ESI-MS. Their catalytic water oxidation properties in the presence of [Ce(NH(4))(2)(NO(3))(6)] (Ce(IV)) as oxidant at pH 1.0 have been investigated. At low concentrations of Ce(IV) (5 mm), high turnover numbers of up to 4500 have been achieved. An (18)O-labelling experiment established that both O atoms in the evolved O(2) originate from water. Combined electrochemical study and electrospray ionisation mass spectrometric analysis suggest that ligand exchange between coordinated 4-picoline and free water produces Ru aquo species as the real water oxidation catalysts.
|
|
| 26. |
|
|
| 27. |
- Xu, Yunhua, 1964-
(författare)
-
Synthesis and Photoinduced Electron Transfer of Donor-Sensitizer-Acceptor Systems
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Artificial systems involving water oxidation and solar cells are promising ways for the conversion of solar energy into fuels and electricity. These systems usually consist of a photosensitizer, an electron donor and / or an electron acceptor. This thesis deals with the synthesis and photoinduced electron transfer of several donor-sensitizer-acceptor supramolecular systems.The first part of this thesis describes the synthesis and properties of two novel dinuclear ruthenium complexes as electron donors to mimic the donor side reaction of Photosystem II. These two Ru2 complexes were then covalently linked to ruthenium trisbipyridine and the properties of the resulting trinuclear complexes were studied by cyclic voltammetry and transient absorption spectroscopy.The second part presents the synthesis and photoinduced electron transfer of covalently linked donor-sensitizer supramolecular systems in the presence of TiO2 as electron acceptors. Electron donors are tyrosine, phenol and their derivatives, and dinuclear ruthenium complexes. Intramolecular electron transfer from the donor to the oxidized sensitizer was observed by transient absorption spectroscopy after light excitation of the Ru(bpy)32+ moiety. The potential applications of Ru2-based electron donors in artificial systems for water oxidation and solar cells are discussed.In the final part, the photoinduced interfacial electron transfer in the systems based on carotenoids and TiO2 is studied. Carotenoids are shown to act as both sensitizers and electron donors, which could be used in artificial systems to mimic the electron transfer chain in natural photosynthesis.
|
|
| 28. |
|
|
| 29. |
|
|
| 30. |
- Yan, Yinglin, et al.
(författare)
-
Waste Office Paper Derived Cellulose-Based Carbon Host in Freestanding Cathodes for Lithium-Sulfur Batteries
- 2022
-
Ingår i: ChemElectroChem. - : John Wiley & Sons. - 2196-0216. ; 9:11
-
Tidskriftsartikel (refereegranskat)abstract
- Due to large sulfur (S) content and simple manufacturing techniques, free-standing cathodes for lithium-sulfur (Li−S) batteries are gaining a lot of attention recently. Waste office paper, which is consumed in large quantities annually, was used to make a free-standing paper-based carbon (FPC) substrate, which inherited fiber-like morphology. In addition, reduced graphene oxide (rGO) nanosheets modified FPC (rGO@FPC) host was also prepared by a vacuum filtration method. After S impregnation, the FPC/S and rGO@FPC/S free-standing cathodes were employed in Li−S batteries. The rGO@FPC/S free-standing cathode exhibited extremely competitive electrochemical performance, including a reversible discharge capacity of 315 mAh g−1 at 0.5 C after 500 cycles. This is due to the uniform S distribution, which boosts the utilization ratio, and the significant blocking action for polysulfide ions, which prevents the redox shuttle effect.
|
|
| 31. |
- Yu, Ze, et al.
(författare)
-
Ruthenium sensitizer with a thienylvinylbipyridyl ligand for dye-sensitized solar cells
- 2011
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 40:33, s. 8361-8366
-
Tidskriftsartikel (refereegranskat)abstract
- A new ruthenium bipyridyl complex, coded as YX360, incorporating a conjugated thienylvinylbipyridyl ligand, cis-Ru(dtbpy)(dcbpy)(NCS)(2) [dtbpy = 4,4'-di(thienylvinyl)-2,2'-bipyridyl; dcbpy = 4,4'-dicarboxy-2,2'-bipyridyl], has been synthesized and studied as a dye in dye-sensitized solar cells (DSCs). The new dye is compared to its precursor N719, which is one of the best ruthenium-based sensitizers known so far. In the dye YX360 the lowest metal-to-ligand charge-transfer (MLCT) band is red-shifted by 10 nm and the molar extinction coefficient is dramatically increased as compared to N719. The reason can largely be attributed to the introduction of the extended pi-conjugation unit to the ruthenium complex. Correspondingly, the incident photon-to-current conversion efficiency (IPCE) spectra of solar cells containing the dye YX360 show relatively higher values in the plateau region and a wider absorption spectrum relative to those of the dye N719. The effect is most pronounced for thinner TiO(2) films, for which comparable overall conversion efficiencies were obtained. However, as the TiO(2) film thickness is increased, DSCs containing N719 show superior conversion efficiencies. Although YX360 typically renders better short-circuit currents, the open-circuit voltage is suppressed because of larger electron recombination losses at the TiO(2)/dye/electrolyte interface. The results highlight that an extended aromatic ligand system in a sensitizing dye on the one hand improved light absorption, but on the other hand more efficiently loses photoelectrons through a recombination pathway via the dye to the electrolyte.
|
|
